1. Field of the Invention
This invention relates to a brake mechanism and more particularly to a brake mechanism associated with a hydraulic circuit and having a removable spring assembly operable to actuate a service brake and apply a preselected braking force to a rotating disc to automatically actuate a park brake in the event of hydraulic failure.
2. Description of the Prior Art
Conventional fluid actuated braking systems which are associated with a hydraulic circuit and are operable to brake the vehicle by applying a braking force upon a rotatable disc require the continued supply of pressurized fluid to actuate the service brake. Furthermore, once the parking brake is engaged, a loss of hydraulic power releases the parking brake, creating an unsafe situation. Thus, if a malfunction should occur which would terminate operation of the fluid pumps, such as a loss in electric power supplied to the electrically powered vehicle, the brake becomes inoperative.
In many cases, when it is required to move an inoperable vehicle having the parking brake engaged, the entire brake assembly must be dismantled to release the parking brake so that the vehicle may be towed. In addition, considerable care must be exercised to prevent explosion of the compressed brake spring. To return the vehicle to service, the brake must be reassembled. Such a procedure is time consuming and, in most cases, produces a variance in the braking force by disturbing the coordination and precision orginally established between interacting components of the brake assembly. If this hazard is to be avoided, the only alternative is replacing the inoperative brake assembly with an operative brake assembly. In most instances, installing a complete brake assembly on a vehicle in a working environment requires considerable effort resulting in loss of vehicle efficiency.
There is need for a brake mechanism operable in a hydraulic circuit that will remain operational in the event of loss of hydraulic power to the system and can be efficiently serviced without requiring extensive repair of the brake mechanism and alteration of the braking force.